(1) Field of the Invention
This invention relates to silver halide color photographic materials and particularly to silver halide color photographic materials which provide a color image having excellent graininess and color reproduction and which have excellent characteristics of development processing.
(2) Description of the Prior Art
As is well-known, silver halide multilayer color photographic materials comprise a support formed of a cellulose ester or a polyester or the like having coated thereon at least one red-sensitive silver halide emulsion layer comprising a nondiffusible cyan dye-forming coupler, at least one green-sensitive silver halide emulsion layer comprising a nondiffusible magenta dye-forming coupler and at least one blue-sensitive silver halide emulsion layer comprising a nondiffusible yellow dye-forming coupler, which layers may further be divided to achieve specific purposes. For example, British Pat. No. 818,687 discloses a photographic material wherein at least one emulsion layer comprises two unit emulsion layers, one of which is a low-speed layer placed near to the support and the other of which is a high-speed layer placed over the low-speed layer to thereby improve the sensitivity of the photographic material. British Pat. No. 923,045 discloses that graininess of a color image may be improved by controlling the maximum color density of a high-speed unit emulsion layer. Japanese Patent Publication No. 49-15495 discloses a high-speed multilayer color photographic material which comprises red-sensitive, green-sensitive and blue-sensitive layers, at least one of which layers comprises three unit emulsion layers, the uppermost layer of which has the highest-speed and the lowermost layer of which has the lowest-speed.
It is known to incorporate into these color photographic materials a compound which reacts with the oxidation products of a color developing agent to release a development restrainer or a precursor thereof, i.e. the so-called DIR compound. Japanese Patent Application (OPI) (unexamined published application) No. 49-42345 discloses incorporation of a DIR coupler into the low-speed emulsion layer of the aforementioned photographic material comprising high- and low-speed emulsion layers and Japanese Patent Application (OPI) No. 53-7230 discloses incorporation of a DIR compound into the medium-speed emulsion layer of the aforementioned photographic material comprising high-, medium- and low-speed emulsion layers.
The incorporation of the DIR compound into the medium-speed emulsion layer (and the removal of the DIR compound from the high-speed emulsion layer) increases sensitivity, improves image graininess or sharpness, or the ratio of sensitivity to graininess and further extends exposure latitude.
Thus, it has been known that a DIR compound improves image graininess or sharpness and color reproduction. A development restrainer released from the DIR compound depending on an image density restrains the development to thereby make the color image particles finer and diffuses in the direction parallel to the emulsion layer to cause the Eberhard effect, improving sharpness, and also in the direction perpendicular to the emulsion layer to cause a development restraining effect on the other emulsion layers, i.e. an interlayer development restraining effect to thereby increase saturation of colors, resulting in an improvement in color reproduction. Japanese Patent Application (OPI) No. 59-131934 discloses that the improvement in image sharpness and color reproduction may be intensified by suitably increasing the distance between the site where a development restrainer is split-off and released during development and the site where the development restrainer works.
In the field of silver halide color photographic materials, particularly materials for photographing, realization of high-quality color images has become a major concern with the current tendency toward miniaturization of cameras.
However, it is known that when a DIR compound is used for improving image sharpness, graininess or color reproduction, such disadvantages as a decrease in sensitivity, flattening of gradation and, occasionally, a retardation in the progress of development occurs due to the development restraining effect of the DIR compound. Various research toward realizing high image quality without such disadvantages, including, for example, investigation into useful DIR compounds, has been conducted but the problems still remain unsolved. The results of such studies are seen, for example, in West German Pat. (OLS) No. 2704797 which discloses a layer structure wherein a layer comprising a DIR compound and a low-speed AgCl emulsion is interposed between a high-speed emulsion layer of a red-sensitive silver halide emulsion layer and that of a green-sensitive silver halide emulsion layer gives a photographic material which is high in sensitivity and exerts a great interlayer development restraining effect even in the area of low density. In the layer structure of this German Patent, a major portion of the development restrainer, which is released from the DIR compound in the interposed layer when it reacts with the oxidation products of a developing agent diffused into the interposed layer from green- or red-sensitive high-speed emulsion layer, is adsorbed on the low-speed silver chloride emulsion layer and contributes little to the development restraining effect on the photosensitive emulsion layer. Further the layer structure has a disadvantage in that the development restraining effect, if any, will be canceled by the development accelerating effect caused by the interaction between a silver bromoiodide emulsion in the photosensitive emulsion layer and the silver chloride emulsion, i.e. trapping of iodide ion by silver chloride or conversion of bromide ion by silver chloride. The photographic material disclosed in Japanese Patent Application (OPI) No. 53-7230 does not have such disadvantages as flattening of gradation or a retardation in the progress of development but it is still unsatisfactory because it is low in the interlayer development restraining effect, whereas it is high in the graininess-improving effect.